Publications by authors named "Ivanna Yau"
Article Synopsis
- Outcomes from vagus nerve stimulation (VNS) improve over time in children with drug-resistant epilepsy, but the benefits of deep brain stimulation (DBS) versus continued VNS optimization were unclear.
- A study involving 18 children aged 8-17 showed that adding DBS after a year of ineffective VNS led to significantly greater seizure reduction (51.9% vs. 12.3%).
- While DBS resulted in fewer bothersome seizures, it did not improve the overall quality of life, suggesting that earlier consideration of DBS could be beneficial for children not responding to VNS.
Background And Objectives: Gelastic seizures due to hypothalamic hamartomas (HH) are challenging to treat, in part due to an incomplete understanding of seizure propagation pathways. Although magnetic resonance imaging-guided laser interstitial thermal therapy (MRgLITT) is a promising intervention to disconnect HH from ictal propagation networks, the optimal site of ablation to achieve seizure freedom is not known. In this study, we investigated intraoperative post-ablation changes in resting-state functional connectivity to identify large-scale networks associated with successful disconnection of HH.
View Article and Find Full Text PDFBackground: Hippocampal sclerosis (HS) is a common surgical substrate in adult epilepsy surgery cohorts but variably reported in various pediatric cohorts.
Objective: We aimed to study the epilepsy phenotype, radiological and pathological variability, seizure and neurocognitive outcomes in children with drug-resistant epilepsy and hippocampal sclerosis (HS) with or without additional subtle signal changes in anterior temporal lobe who underwent surgery.
Methods: This retrospective study enrolled children with drug-resistant focal epilepsy and hippocampal sclerosis with or without additional subtle T2-Fluid Attenuated Inversion Recovery (FLAR)/Proton Density (PD) signal changes in anterior temporal lobe who underwent anterior temporal lobectomy with amygdalohippocampectomy.
Article Synopsis
- The epilepsy monitoring unit (EMU) can experience unnoticed changes in cognitive and behavioral health due to medical and environmental factors.
- The psychomotor vigilance task (PVT) was tested on seven children in the EMU, linking their performance to seizure counts, medication levels, and sleep quality.
- Findings showed that performance on the PVT was negatively affected by increased antiseizure medications and epileptiform activity, suggesting this task could help monitor patient responses and guide clinical choices.
Article Synopsis
- Epilepsy care in Ontario faces significant challenges including limited bed availability in Epilepsy Monitoring Units (EMU), restricted surgical options, and inadequate community support, especially following the COVID-19 pandemic.* -
- A 44-item survey was conducted across all 11 adult and pediatric epilepsy centers in Ontario, collecting both quantitative and qualitative data on the current state of epilepsy care.* -
- Findings showed persistent gaps in care due to EMU bed pressures and workforce shortages, prompting the formation of a clinical network to help improve access to epilepsy services in the region.*
Stimulation-Induced Seizures in Children Undergoing Stereo-EEG Evaluation.
J Clin Neurophysiol
February 2025
Article Synopsis
- The study explored the effectiveness of low-frequency stimulation in inducing seizures in children with drug-resistant epilepsy during stereo-EEG evaluations.
- A total of 14 children, primarily aged around 13, underwent cortical stimulation with specific parameters and were monitored for seizure activity.
- The results showed that about 29% of the participants experienced habitual seizure activity from this method, highlighting its potential as a tool in understanding and treating focal epilepsy in pediatric patients.
Article Synopsis
- Hippocampal Sclerosis (HS) can occur alongside other brain lesions in children, leading to persistent seizures even after functional hemispherectomy (FH), a surgical procedure to remove one hemisphere of the brain.
- A retrospective study identified three children who developed contralateral HS after undergoing FH for unilateral cortical malformations, all of whom continued to experience seizures post-surgery.
- The research suggests that the underlying mechanisms for contralateral HS in these cases are unclear, but genetic mutations may influence seizure outcomes after epilepsy surgery.
Children with epilepsy commonly have comorbid neurocognitive impairments that severely affect their psychosocial well-being, education, and future career prospects. Although the provenance of these deficits is multifactorial, the effects of interictal epileptiform discharges (IEDs) and anti-seizure medications (ASMs) are thought to be particularly severe. Although certain ASMs can be leveraged to inhibit IED occurrence, it remains unclear whether epileptiform discharges or the medications themselves are most deleterious to cognition.
View Article and Find Full Text PDFObjective: The antiseizure effects of vagus nerve stimulation (VNS) are thought to be mediated by the modulation of afferent thalamocortical circuitry. Cross-frequency phase-amplitude coupling (PAC) is a mechanism of hierarchical network coordination across multiple spatiotemporal scales. In this study, we leverage local field potential (LFP) recordings from the centromedian (CM) (n = 3) and anterior (ATN) (n = 2) nuclei in five patients with tandem thalamic deep brain stimulation and VNS to study neurophysiological changes in the thalamus in response to VNS.
View Article and Find Full Text PDFObjective: Working memory deficits are prevalent in childhood epilepsy. Working memory processing is thought to be supported by the phase of hippocampal neural oscillations. Disruptions in working memory have previously been linked to the occurrence of transient epileptic activity.
View Article and Find Full Text PDFDespite decades of clinical usage, selection of patients with drug resistant epilepsy who are most likely to benefit from vagus nerve stimulation (VNS) remains a challenge. The mechanism of action of VNS is dependent upon afferent brainstem circuitry, which comprises a critical component of the Vagus Afferent Network (VagAN). To evaluate the association between brainstem afferent circuitry and seizure response, we retrospectively collected intraoperative data from sub-cortical recordings of somatosensory evoked potentials (SSEP) in 7 children with focal drug resistant epilepsy who had failed epilepsy surgery and subsequently underwent VNS.
View Article and Find Full Text PDFPurpose: Deep brain stimulation (DBS) is a common tool for the treatment of movement disorders in adults; however, it remains an emerging treatment modality in children with a growing number of indications, including epilepsy and dystonia. The Child & Youth CompreHensIve Longitudinal Database of DBS (CHILD-DBS) study aims to prospectively collect relevant data on quality of life (QoL), safety, efficacy, and long-term neurodevelopmental outcomes following DBS in children.
Methods: Data are collected and managed using the Research Electronic Data Capture (REDCap).
Article Synopsis
- The study aimed to evaluate the long-term cognitive effects of cerebral sinovenous thrombosis (CSVT) in children using neuropsychological tests on abilities like IQ, attention, and language.
- Results showed that kids with CSVT scored significantly lower than average on tests measuring full-scale IQ, working memory, and processing speed, with additional challenges noted in executive function and language.
- Factors such as presenting with seizures or incomplete recanalization may increase the likelihood of cognitive issues, indicating a need for larger studies to identify specific predictors of deficits in these children.
Purpose: This study evaluated the seizure outcomes in children with drug-resistant epilepsy (DRE), having a pre-existing VNS device, after generator replacement with cardiac-based VNS device.
Methods: This retrospective study enrolled 30 children with DRE from 2 centers with an existing VNS device nearing end-of-service who underwent generator replacement with cardiac-based VNS device and had at least 1 year follow up. Seizure outcomes and adverse effects were studied.
There is an unmet need to develop robust predictive algorithms to preoperatively identify pediatric epilepsy patients who will respond to vagus nerve stimulation (VNS). Given the similarity in the neural circuitry between vagus and median nerve afferent projections to the primary somatosensory cortex, the current study hypothesized that median nerve somatosensory evoked field(s) (SEFs) could be used to predict seizure response to VNS. Retrospective data from forty-eight pediatric patients who underwent VNS at two different institutions were used in this study.
View Article and Find Full Text PDFArticle Synopsis
- Advanced dynamic statistical parametric mapping (AdSPM) was utilized with magnetoencephalography (MEG) to detect epileptogenic lesions in a 15-year-old girl who had MRI-negative focal-onset epilepsy unresponsive to medications.
- The patient's seizures included two types: one triggered from sleep with specific movements and the other starting with dizziness, both shown to originate in the right frontal region through EEG and MEG studies.
- Following the identification of the seizure source, the patient underwent surgical resection, was diagnosed with focal cortical dysplasia type IIB, and has remained seizure-free for 2 years on treatment.
Objective: Vagus nerve stimulation (VNS) is a common treatment for medically intractable epilepsy, but response rates are highly variable, with no preoperative means of identifying good candidates. This study aimed to predict VNS response using structural and functional connectomic profiling.
Methods: Fifty-six children, comprising discovery (n = 38) and validation (n = 18) cohorts, were recruited from 3 separate institutions.
Objective: Polymicrogyria (PMG) is a common malformation of cortical development. Many patients with PMG will have medically refractory epilepsy but the role of epilepsy surgery is unclear. The objective of this study was to assess the efficacy of surgical resection/disconnection in achieving seizure control in pediatric patients with PMG.
View Article and Find Full Text PDFObjective: Limited evidence on the relationship between antiepileptic drug (AED) tapering and the likelihood of a seizure during an Epilepsy Monitoring Unit (EMU) admission is available, and no evidence specific to the pediatric population has been published. Our study sought to determine whether AED tapering leads to increased seizure likelihood in a pediatric EMU setting.
Methods: We performed a retrospective chart review of children admitted to the pediatric EMU at the Hospital for Sick Children in Toronto between June 1, 2014 and June 1, 2016.
Background And Purpose: Arteriopathy is common in childhood arterial ischemic stroke (AIS) and predicts stroke recurrence. Currently available vascular imaging techniques mainly image the arterial lumen rather than the vessel wall and have a limited ability to differentiate among common arteriopathies. We aimed to investigate the value of a magnetic resonance imaging-based technique, namely noninvasive arterial wall imaging (AWI), for distinguishing among arteriopathy subtypes in a consecutive cohort of children presenting with AIS.
View Article and Find Full Text PDFBackground: The presence of cerebral astrocytic inclusions recently has been described in a subset of children with early-onset refractory epilepsy, with or without structural brain malformations, and varying degrees of developmental delay.
Methods: We describe two new individuals with epilepsy with astrocytic inclusions and suggest that in some children this disorder may represent a unique hemispheric epilepsy. We review previously reported individuals with epilepsy with astrocytic inclusions.
Aim: We aimed to evaluate whether an institutional acute stroke protocol (ASP) could accelerate the diagnosis and secondary treatment of pediatric stroke.
Method: We initiated an ASP in 2005. We compared 209 children (125 males, 84 females; median age 4.